Temporary plugging agent for fracturing as well as preparation method and application of temporary plugging agent

Abstract

The invention discloses a temporary plugging agent for fracturing and a preparation method and application thereof, and the preparation method of the temporary plugging agent for fracturing comprises the following steps: respectively taking the following raw materials in percentage by weight: an acrylamide monomer, ammonium persulfate, methylene bisacrylamide, xanthan gum powder, a cross-linking agent and tetrakis hydroxymethyl phosphonium sulfate; the preparation method comprises the following steps: mixing the raw materials in a protective gas atmosphere, reacting to obtain colloid A, and crushing the colloid A to obtain colloid A powder; the preparation method comprises the following steps: respectively weighing the following raw materials in percentage by weight: colloid A powder, melamine, glycerol, polyvinyl alcohol, an ammonium persulfate capsule gel breaker, a high-temperature additive and calcium silicate, mixing, heating and stirring the obtained mixture until the mixture is completely molten to form a mixture B, cooling the mixture B, and crushing the cooled mixture B into particles to obtain the temporary plugging agent for fracturing. The prepared temporary plugging agent for fracturing has excellent plugging pressure, is self-degradable at high temperature, is easy to flow back, and reduces damage to strata.

Description

Technical Field

[0001] The present invention belongs to the field of temporary plugging agents for oilfield development, and particularly relates to a temporary plugging agent for fracturing, a preparation method thereof, and an application thereof. Background Art

[0002] The horizontal well volume fracturing technology is an effective means for the economic development of unconventional oil and gas. Forming complex fracture networks and improving fracture complexity are the keys for shale reservoirs to obtain industrial oil and gas flows. During the fracturing process of oil and gas wells, injecting temporary plugging agents into the wellbore can achieve the purpose of layered fracturing. For the layered fracturing operation of open-hole horizontal wells, injecting temporary plugging agents multiple times is beneficial to achieving multiple fractures within a section. The temporary plugging turns and fractures to block the original fractures, realizing fracture diversion and forming new fractures, thereby forming a complex fracture network system, increasing the fracture drainage area, and achieving the purpose of production increase. Currently, most shale gas reservoirs adopt the fine segmented fracturing and reconstruction process. However, microseismic monitoring technology, production profile testing technology, tracer testing technology, etc. show that many perforation clusters have not been fully reconstructed due to factors such as stress differences and casing deformation, seriously affecting the single-well production. For economically exploited oilfields with reservoir temperature ranges roughly between 30 - 230 °C, there is currently no product series that can simultaneously achieve both wellbore plugging and in-fracture plugging across the entire temperature range. There are only products for single wellbore plugging or in-fracture plugging. Although the knot-type wellbore temporary plugging agent has excellent performance and good plugging effect, its cost is too high, and it cannot simultaneously achieve in-fracture plugging and fracturing. Summary of the Invention

[0003] In order to solve the above technical problems, one of the purposes of the present invention is to provide a preparation method of a temporary plugging agent for fracturing. The temporary plugging agent for fracturing has excellent plugging pressure, low residue content after transformation, is easy to flow back, and reduces damage to the formation.

[0004] In order to achieve the above purpose, the technical solution of the present invention is as follows: A preparation method of a temporary plugging agent for fracturing includes the following steps:

[0005] Step 1: Weigh and take the following raw materials respectively by weight percentage: acrylamide monomer 10 - 50 wt%, ammonium persulfate 0.01 - 3 wt%, methylene bisacrylamide 0.01 - 2 wt%, xanthan gum powder 0.1 - 3 wt%, crosslinking agent 0.01 - 1 wt%, and tetrakis(hydroxymethyl)phosphonium sulfate 0.5 - 5 wt%. The balance is solvent water. Mix them under a protective gas atmosphere, and obtain colloid A after the reaction. Cut, dry, and crush colloid A to obtain colloid A powder;

[0006] Step 2: Weigh and take the following raw materials respectively by weight percentage: 50 wt% of colloid A powder, 3 - 13 wt% of melamine, 3 - 13 wt% of glycerol, 20 - 26 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker, 0 - 20 wt% of high - temperature additive, and 3 wt% of calcium silicate, and mix them. Heat the obtained mixture to above 200 °C, stir until completely melted to form mixture B, cool mixture B, and pulverize it into granular form after cooling to obtain the temporary plugging agent for fracturing.

[0007] The cross - linker is organic boron, organic zirconium, organic chromium or organic boron zirconium.

[0008] The high - temperature additive is polylactic acid or polyglycolic acid.

[0009] In step 1, the reaction temperature is 30 - 60 °C, and after the reaction, it is kept warm for at least 8 h to obtain colloid A.

[0010] Preferably, in step 1, the dosages of each raw material by weight percentage are respectively: 10 wt% of acrylamide monomer, 0.5 wt% of ammonium persulfate, 0.02 wt% of methylene bisacrylamide, 1 wt% of xanthan gum powder, 0.03 wt% of cross - linker, and 2 wt% of tetramethylol phosphonium sulfate, with the balance being water; in step 2, the dosages of each raw material by weight percentage are respectively: 50 wt% of colloid A powder, 13 wt% of melamine, 13 wt% of glycerol, 20 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker, and 3 wt% of calcium silicate, and they are mixed.

[0011] Preferably, in step 1, the dosages of each raw material by weight percentage are respectively: 20 wt% of acrylamide monomer, 0.08 wt% of ammonium persulfate, 0.02 wt% of methylene bisacrylamide, 1 wt% of xanthan gum powder, 0.03 wt% of cross - linker, and 2 wt% of tetramethylol phosphonium sulfate, with the balance being water; in step 2, the dosages of each raw material by weight percentage are respectively: 50 wt% of colloid A powder, 10 wt% of melamine, 10 wt% of glycerol, 26 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker, and 3 wt% of calcium silicate, and they are mixed.

[0012] Preferably, in step 1, the dosages of each raw material by weight percentage are respectively: 30 wt% of acrylamide monomer, 0.06 wt% of ammonium persulfate, 0.02 wt% of methylene bisacrylamide, 1 wt% of xanthan gum powder, 0.03 wt% of cross - linker, and 2 wt% of tetramethylol phosphonium sulfate, with the balance being water; in step 2, the dosages of each raw material by weight percentage are respectively: 50 wt% of colloid A powder, 5 wt% of melamine, 5 wt% of glycerol, 20 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker, 16 wt% of high - temperature additive, and 3 wt% of calcium silicate, and they are mixed.

[0013] Preferably, the dosages of the raw materials in step 1 are measured by weight percentage as follows: acrylamide monomer 40 wt%, ammonium persulfate 0.04 wt%, methylene bisacrylamide 0.02 wt%, 1 wt% xanthan gum powder, crosslinking agent 0.03 wt%, and tetramethylol phosphonium sulfate 2 wt%, with the balance being water; the dosages of the raw materials in step 2 are measured by weight percentage as follows: 50 wt% of colloid A powder, 3 wt% of melamine, 3 wt% of glycerol, 20 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker, 20 wt% of high-temperature assistant, and 3 wt% of calcium silicate are mixed.

[0014] A second object of the present invention is to provide a temporary plugging agent for fracturing prepared by the above-mentioned preparation method.

[0015] A third object of the present invention is to provide an application of the above-mentioned temporary plugging agent for fracturing as a hole plugging agent for reservoirs at 30 - 230 °C during the fracturing exploitation process of oil and gas wells.

[0016] The beneficial effects of the present invention are as follows: (1) The temporary plugging agent for fracturing provided in this embodiment has the characteristic of being completely degradable, can be used for temporarily plugging hole plugs and interlayer fractures in reservoirs at 30 - 230 °C, has excellent plugging pressure, self-degrades at high temperature, is easy to flow back, and reduces damage to the formation;

[0017] (2) The temporary plugging agent provided in this embodiment can withstand a pressure of 70 MPa for more than 30 minutes during hole plugging, and the dissolution rate is 100%. It meets the requirements of diversion fracturing at 30 - 230 °C and has a wide use temperature range;

[0018] (3) The temporary plugging agent provided in this embodiment can be simultaneously applied to temporary hole plugging and temporary plugging in interlayer fractures. The preparation method of this temporary plugging agent is simple, easy to operate, and has a low cost, and has good economic popularization value. Description of the Drawings

[0019] Figure 1 It is a construction curve graph in the application example of the present invention. Detailed Embodiments

[0020] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0021] Example 1

[0022] This embodiment provides a temporary plugging agent for fracturing, and its preparation method includes the following steps:

[0023] Step 1: Weigh and separately take the following raw materials by weight percentage: acrylamide monomer 10 wt%, ammonium persulfate 0.5 wt%, methylene bisacrylamide 0.02 wt%, xanthan gum powder 1 wt%, crosslinking agent 0.03 wt% (organic boron), and tetramethylol phosphonium sulfate 2 wt%, with the balance being water. Mix them at 30 °C under a nitrogen atmosphere, react and keep warm for 8 hours to obtain Colloid A. After cutting, drying, and pulverizing Colloid A, Colloid A powder is obtained.

[0024] Step 2: Weigh and separately take the following raw materials by weight percentage: 50 wt% of Colloid A powder, 13 wt% of melamine, 13 wt% of glycerol, 20 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker, and 3 wt% of calcium silicate, and mix them. Heat the resulting mixture to above 200 °C, stir until completely melted to form Mixture B. Cool Mixture B, and after cooling, dry it (place it in an oven, dry at 75 °C for 48 h), and pulverize it into granular form (different specifications of temporary plugging agents can be obtained according to different particle sizes of the particles), and then the temporary plugging agent for fracturing is obtained.

[0025] <Performance Test>

[0026] (1) Solubility Experiment

[0027] Add about 3 g of the temporary plugging agent to a stoppered test tube, add water to 100 g (i.e., the mass fraction of the temporary plugging agent is 3%), and measure the complete dissolution time of the temporary plugging agent with different particle sizes at different temperatures. The results are shown in Table 1. The specific results show that the dissolution time of the temporary plugging agent is affected by the particle size and dissolution temperature, but it can be completely dissolved within 48 hours without residue and without harm to the formation.

[0028] Table 1 Dissolution Time of Temporary Plugging Agents with Different Particle Sizes

[0029] Particle size / mm Dissolution time for 50% at 30℃ / h Complete dissolution time at 30℃ / h 1 - 6mm 8 20 13mm 16 36

[0030] (2) Pressure Resistance and Plugging Performance Experiment

[0031] Select 40 / 70-mesh quartz sand and fill the sand-packed tube in a wet filling method, with a permeability of about 2000 mD. Leave a 10-mm gap at the injection end of the sand-packed tube, fill it with temporary plugging agent particles, and conduct a water injection experiment at 5 mL / min at different temperatures. Use the maximum injection pressure to characterize the plugging breakthrough pressure. The results are shown in Table 2. The specific results show that this temporary plugging agent can form an effective filter cake, plug the high-permeability channel, has a strong plugging effect, can withstand high pressure, and the maximum breakthrough pressure at 30 °C reaches 22.13 MPa, playing an effective plugging role and having a good plugging effect.

[0032] Table 2 Breakthrough Pressure of Temporary Plugging Agents with Different Particle Sizes

[0033]

[0034] Example 2

[0035] Same as Example 1, with the differences being that:

[0036] In Step 1, the dosage of acrylamide monomer is 20 wt%, the dosage of ammonium persulfate is 0.08 wt%, and the crosslinking agent is organic chromium;

[0037] In Step 2, the dosage of melamine is 10 wt%, the dosage of glycerol is 10 wt%, and the dosage of polyvinyl alcohol is 26 wt%, and the other raw materials and dosages remain unchanged.

[0038] <Performance Test>

[0039] (1) The results of the solubility experiment are shown in Table 3. The results indicate that the dissolution time of the temporary plugging agent is affected by the particle size and dissolution temperature, and it can completely dissolve within 48 hours without residue and cause no harm to the formation.

[0040] Table 3 Dissolution Time of Temporary Plugging Agents with Different Particle Sizes

[0041] Particle size / mm Dissolution time for 50% at 80℃ / h Complete dissolution time at 80℃ / h 1 - 6mm 7 16 13mm 11 24

[0042] (2) The results of the pressure resistance and plugging performance experiment are shown in Table 4. The results indicate that the temporary plugging agent can form an effective filter cake, plug the high-permeability channel, has a strong plugging effect, can withstand high pressure, and the maximum breakthrough pressure reaches 31.01 MPa at 80 °C, playing an effective plugging role and having a good plugging effect.

[0043] Table 4 Breakthrough Pressure of Temporary Plugging Agents with Different Particle Sizes

[0044]

[0045] Example 3

[0046] Same as Example 1, with the differences being that:

[0047] In Step 1, the dosage of acrylamide monomer is 30 wt%, the dosage of ammonium persulfate is 0.06 wt%, and the crosslinking agent is organic boron zirconium;

[0048] In Step 2, the dosage of melamine is 5 wt%, the dosage of glycerol is 5 wt%, the dosage of polyvinyl alcohol is 20 wt%, and 16 wt% of polylactic acid (high-temperature additive) is also added, and the other raw materials and dosages remain unchanged.

[0049] <Performance Test>

[0050] (1) The results of the solubility experiment are shown in Table 5. The results indicate that the dissolution time of the temporary plugging agent is affected by the particle size and dissolution temperature, and it can completely dissolve within 48 hours without residue and cause no harm to the formation.

[0051] Table 5 Dissolution time of temporary plugging agents with different particle sizes

[0052] Particle size / mm Dissolution time for 50% at 150℃ / h Complete dissolution time at 150℃ / h 1 - 6mm 6 10 13mm 10 21

[0053] (2) The results of the pressure resistance and plugging performance experiment are shown in Table 6. The results indicate that the temporary plugging agent can form an effective filter cake, plug the high-permeability channels, has a strong plugging effect, can withstand high pressure, and the maximum breakthrough pressure reaches 27.61 MPa at 30 °C, playing an effective plugging role and having a good plugging effect.

[0054] Table 6 Breakthrough pressure of temporary plugging agents with different particle sizes

[0055]

[0056] Example 4

[0057] Same as Example 1, the differences are as follows:

[0058] In Step 1, the dosage of acrylamide monomer is 40 wt%, the dosage of ammonium persulfate is 0.04 wt%, and the crosslinking agent is organic zirconium;

[0059] In Step 2, the dosage of melamine is 3 wt%, the dosage of glycerol is 3 wt%, the dosage of polyvinyl alcohol is 20 wt%, and 20 wt% of polyglycolic acid (high-temperature additive) is also added, with other raw materials and dosages remaining unchanged.

[0060] <Performance Test>

[0061] (1) The results of the solubility experiment are shown in Table 7. The results indicate that the dissolution time of the temporary plugging agent is affected by the particle size and dissolution temperature, and it can completely dissolve within 48 hours without residue, causing no harm to the formation.

[0062] Table 7 Dissolution time of temporary plugging agents with different particle sizes

[0063] Particle size / mm Dissolution time for 50% at 230℃ / h Complete dissolution time at 230℃ / h 1 - 6mm 4 9 13mm 8 17

[0064] (2) The results of the pressure resistance and plugging performance experiment are shown in Table 8. The results indicate that the temporary plugging agent can form an effective filter cake, plug the high-permeability channels, has a strong plugging effect, can withstand high pressure, and the maximum breakthrough pressure reaches 16.71 MPa at 230 °C, playing an effective plugging role and having a good plugging effect.

[0065] Table 8 Breakthrough pressure of temporary plugging agents with different particle sizes

[0066]

[0067] Application Example

[0068] For a certain shale gas, on December 22, 2021, a degradable temporary plugging agent for fracturing was used in the fracturing construction of Well XX. Figure 1It is a construction curve graph. Fracturing interval of an oil well: 1065.6 - 1074 m, slickwater volume fracturing, 0.2% linear gel working fluid is used to temporarily plug the fracture system formed by fracturing, construction pressure 25.1 - 40.3 MPa, construction displacement 2.8 - 3.0 m 3 / min, total liquid volume 140 m 3 , total sand volume 20 m 3 . During construction, the dosage of the composite temporary plugging agent is 240 kg, the daily oil production before fracturing is 0.2 t / day, and the daily oil production after fracturing is 4.4 t / day, with the stimulation effect being significantly improved. It can be seen that the degradable temporary plugging agent provided by the present invention has good plugging performance.

[0069] Among them, Figure 1 the ordinate unit corresponding to the pressure (construction pressure) is MPa, the ordinate unit of the displacement (construction displacement) is m 3 / min, and the ordinate unit of the sand ratio is ‰.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a temporary plugging agent for fracturing, characterized in that: The steps include: Step 1: taking the following raw materials respectively by weight percentage: 10-50wt% of acrylamide monomer, 0.01-3wt% of ammonium persulfate, 0.01-2wt% of methylene bisacrylamide, 0.1-3wt% of xanthan gum powder, 0.01-1wt% of a cross-linking agent and 0.5-5wt% of tetrakis(hydroxymethyl)phosphonium sulfate, and the balance being water, mixing them under a protective gas atmosphere, and obtaining colloid A after reaction, and obtaining colloid A powder after shearing, drying and crushing the colloid A; Step 2: The following raw materials are measured by weight percentage: 50wt% of colloid A powder, 3-13wt% of melamine, 3-13wt% of glycerol, 20-26wt% of polyvinyl alcohol, 1wt% of ammonium persulfate capsule breaker, 0-20wt% of high-temperature auxiliary agent and 3wt% of calcium silicate are mixed, the obtained mixture is heated to above 200° C., stirred to completely melt to form a mixture B, the mixture B is cooled, and crushed into particles after cooling to obtain a temporary plugging agent for fracturing.

2. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: The cross-linking agent is organic boron, organic zirconium, organic chromium or organic boron zirconium.

3. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: The high temperature auxiliary agent is polylactic acid or polyglycolic acid.

4. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: In the step 1, the reaction temperature is 30-60° C., and the reaction is kept warm for at least 8 hours after the reaction is completed to obtain colloid A.

5. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: The amounts of the raw materials used in step 1 are measured by weight percentage as follows: 10 wt% acrylamide monomer, 0.5 wt% ammonium persulfate, 0.02 wt% methylene bisacrylamide, 1 wt% xanthan gum powder, 0.03 wt% cross-linking agent and 2 wt% tetrakis(hydroxymethyl)phosphonium sulfate, with the remainder being water; the amounts of the raw materials used in step 2 are measured by weight percentage as follows: 50 wt% colloid A powder, 13 wt% melamine, 13 wt% glycerol, 20 wt% polyvinyl alcohol, 1 wt% ammonium persulfate capsule breaker and 3 wt% calcium silicate mixed.

6. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: The amounts of the raw materials used in step 1 are measured by weight percentage as follows: 20 wt% of acrylamide monomer, 0.08 wt% of ammonium persulfate, 0.02 wt% of methylene bisacrylamide, 1 wt% of xanthan gum powder, 0.03 wt% of cross-linking agent and 2 wt% of tetrakis(hydroxymethyl)phosphonium sulfate, with the remainder being water; the amounts of the raw materials used in step 2 are measured by weight percentage as follows: 50 wt% of colloid A powder, 10 wt% of melamine, 10 wt% of glycerol, 26 wt% of polyvinyl alcohol, 1 wt% of ammonium persulfate capsule breaker and 3 wt% of calcium silicate mixed.

7. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: The amounts of the raw materials used in step 1 are measured by weight percentage as follows: 30 wt% acrylamide monomer, 0.06 wt% ammonium persulfate, 0.02 wt% methylene bisacrylamide, 1 wt% xanthan gum powder, 0.03 wt% cross-linking agent and 2 wt% tetrakis(hydroxymethyl)phosphonium sulfate, with the remainder being water; the amounts of the raw materials used in step 2 are measured by weight percentage as follows: 50 wt% colloid A powder, 5 wt% melamine, 5 wt% glycerol, 20 wt% polyvinyl alcohol, 1 wt% ammonium persulfate capsule breaker, 16 wt% high temperature auxiliary agent and 3 wt% calcium silicate mixed.

8. The method for preparing a temporary plugging agent for fracturing according to claim 1, characterized in that: The amounts of the raw materials used in step 1 are measured by weight percentage as follows: 40 wt% acrylamide monomer, 0.04 wt% ammonium persulfate, 0.02 wt% methylene bisacrylamide, 1 wt% xanthan gum powder, 0.03 wt% cross-linking agent and 2 wt% tetrakis(hydroxymethyl)phosphonium sulfate, with the remainder being water; the amounts of the raw materials used in step 2 are measured by weight percentage as follows: 50 wt% colloid A powder, 3 wt% melamine, 3 wt% glycerol, 20 wt% polyvinyl alcohol, 1 wt% ammonium persulfate capsule breaker, 20 wt% high temperature auxiliary agent and 3 wt% calcium silicate mixed.

9. A temporary plugging agent for fracturing, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the temporary plugging agent for fracturing as claimed in claim 9, characterized in that: The temporary plugging agent for fracturing can be used as a temporary plugging agent for blastholes in 30-230°C reservoirs during the fracturing production process of oil and gas wells.

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